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Physics IGCSE > 5 Nuclear physics (5.1 -5.2.2) > Flashcards

5 Nuclear physics (5.1 -5.2.2) Flashcards

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1
Q

structure of an atom

A

a positively charged nucleus and negatively
charged electrons in orbit around the nucleus

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2
Q

how may atoms form positive ions?

A

by losing electrons

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3
Q

how may atoms form negative ions?

A

by gaining electrons

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4
Q

relative charges of protons, neutrons, and electrons

A

proton: +1
neutron: 0
electron: -1

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5
Q

proton number/atomic number

A

number of protons in the nucleus
(number of protons in a neutral atom should be the same as number of electrons)

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6
Q

mass number/nucleon number

A

sum of the number of protons and neutrons in the nucleus

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7
Q

Nuclides

A

type of atom with a specific number of neutrons and protons

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8
Q

nuclide notation

A

chemical symbol: X
proton number Z
nucleon number: A

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9
Q

to find number of neutrons

A

nucleon number - proton number

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10
Q

isotope

A

are atoms of the same element that have equal number of protons but a different number of neutrons

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11
Q

why do isotopes tend to be more unstable?

A

due to their imbalance of protons nad neutrons
- more likely to decay to achieve stability

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12
Q

How does rutherford’s experiement provide evidence for:
a very small nucleus surrounded by mostly empty space

A

A majority of them go through the atom, because the atom is mostly empty space
While a very small number are deflected back because the nucleus is very small

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13
Q

How does rutherford’s experiement provide evidence for:
A nucleus containing most of the mass of the atom

A

Some of the a-particles scattered back, caused by the small, dense nucleus

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14
Q

How does rutherford’s experiement provide evidence for:
A nucleus that is positively charged

A

Some alpha particles are deflected through small atoms
Happens because the positive alpha particles are repelled by the positive nucleus which contains most of the mass

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15
Q

Rutherford’s experiment procedure

A

Scattering of alpha particles by a sheet of thin metal

(Expected - alpha particles to travel through the gold foil and maybe change direction a small amount)

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16
Q

Results of rutherford’s experiment

A
  • most of the alpha particles PASSED STRAIGHT THROUGH the foil
  • some of the alpha particles CHANGED DIRECTION but continued through the foil
  • a few of the alpha particles BOUNCED BACK off the gold foil
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17
Q

ionisation

A

the addition or removal of an electron from an atom

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18
Q

Nuclear fission

A

the splitting of a large, unstable nucleus into two smaller nuclei

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19
Q

Nuclear fission process

A

a neutron collides with an unstable nucleus, causing the nucleus to split into two smaller nuclei (daughter nuclei) as well as two or three neutrons
- gamma rays are emitted

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20
Q

How to know if an nuclide equation is fission

A

there’s a neutron on the left and two daughter nuclei on the right

21
Q

Nuclear fusion

A

when two light nuclei join to form a heavier nucleus

22
Q

why is nuclear fusion hard to reproduce on earth

A

requires extremely high temperatures to maintain
- happens in stars

23
Q

Example of a nuclear fusion equation

A

Two hydrogen nuclei fusing to form a helium nucleus

24
Q

where does the energy for nuclear fusion come from

A

a very small amount of the particles mass is being converted to energy
- E = mc^2
(energy = mass x speed of light squared)

25
Q

background radiation

A

the radiation that exists around us at all times

26
Q

sources that make a significant contribution to background radiation

A

a) radon gas (in the ari)
b) rocks and buildings
c) rood and drink
d) cosmic rays

27
Q

How can ionising radiation be measured

A

using a detector connected to a counter

28
Q

what is count rate

A

number of decays per second (counts/s)

29
Q

Examples of devices used to measure ionising radiation

A

Geiger-Muller tube (or GM tube)
Photographic film
Ionisation chamber
scintillation counters
spark counters

30
Q

Issues using radioactive isotopes with long half lives to release energ

A

ECONOMIC
- high cost of storage
- reduction in touirsm
- loss of farming produce
- reduction of land
SOCIAL
- fear of cancer
- sickness in people/animals
ENVIRONMENTAL
- crop mutation
- leakage into water supplies

31
Q

when is an atom unstable?

A

when it doesn’t have enough binding energy to hold the nucleus together permanently due to the imbalance of neutrons and protons

32
Q

Describe the emission of radiation

A

spontaneous and random in direction

33
Q

Alpha particles (what, charge, range, penetration and ionisation)

A

What: helium nucleus (2 protons and 2 neutrons)
Charge: 2+
Range in air: few cm
Penetration: stopped by paper
Ionisation: High

34
Q

Beta particles (what, charge, range, penetration and ionisation)

A

What: fast-moving electron
Charge: -1
Range in air: few 10s of cm
Penetration: stopped by as few mm of aluminium
Ionisation: medium

35
Q

Gamma rays (what, charge, range, penetration and ionisation)

A

What: EM wave
Charge: 0
Range in air: infinite
Penetration: REDUCED by a few mm of lead
Ionisation: low

36
Q

What do ionising effects depend on

A

Kinetic energy and Electric charge

37
Q

How does kinetic energy affect the ionisation effect?

A

Higher the kinetic energy of the raidaiton, the more ionising it is
- alpha has highest mass and is most ionising (think 1/2mv^2)

38
Q

How does electric charge affect the ionisation effect?

A

Greater the charge the more ionising
- alpha has largest charge and is most ionising

39
Q

Alpha particles and ionising effect

A

Most ionising : they leave a dense trail of ions behind them, affecting virtually every atom they meet, because of this they lose their energy and so have a short range
(short range = relatively harmlessm but dangerous if ingested)

40
Q

When will a particle be deflected in an electric field

A

if it has charge
(so not gamma)

41
Q

When will a particle be deflected in a magnetic field

A

if it has charge and is moving perpendicular to it

42
Q

Alpha particles are deflected towards what (magnetic field)

A

the negative plate as they have a positive charge

43
Q

Beta particles are deflected to what (magnetic filed)

A

positive plate as they have negative charge

44
Q

Gamma rays are deflected to what (magnetic field)

A

Not deflected, travels straight between the plates as they have no charge

45
Q

Why are alpha particles deflected less (and travel further) than beta particles in magnetic fields

A

Alpha particles are heavier than beta particles

46
Q

radioactive decay

A

change in an unstable nucleus that can result in the emission of alpha particles or beta particles or gamma radiation
- changes are spontaneous and random

47
Q

what happens to the nucleus during alpha or beta decay

A

the nucleus changes to that of a different element

48
Q

define half life (of a particular isotope)

A

the time taken for half the nuclei of that isotope in any sample to decay

Physics IGCSE (20 decks)

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